Use toList(growable: false) more

[srawlins]

I looked through every toList() call, for the ones which could be growable: false, and looked at Observatory's allocation profile, before and after, when documenting package:collection. Here are the result of 3 runs, excluding a 4th run outlier:

• Used MB: 444 (before) ⟶ 411 (after) -- 7% reduction
• Allocated MB: 464 (before) ⟶ 450 (after) -- 3% reduction
• _List instance MBs: 149 (before) ⟶ 129 (after) -- 13% reduction
• _List instances: 868510 (before) ⟶ 870317 (after) -- 0% reduction
• _GrowableList instance MBs: 15.1 (before) ⟶ 13.3 (after) -- 12% reduction
• _GrowableList instances: 495092 (before) ⟶ 435337 (after) -- 12% reduction

I can't super explain these. The reduction in _GrowableLists is expected. But why did the MBs of _List also shrink dramatically? 🤷

[keertip]

👍

[mkustermann]

I can't super explain these. The reduction in _GrowableLists is expected. But why did the MBs of _List also shrink dramatically? 🤷

Growable list is a wrapper object and a backing store. The backing store grows by power-of-2. By switching to non-growable list, you avoid the wrapper object and shrink the backing store to the precise length you need it (modulo some VM-specifics, we round up to even number of slots).

[srawlins]

Ah perfect, thanks so much for the explanation!